Environmental and exergoeconomic assessments of a novel biomass gasification based solid oxide fuel cell and heat engine hybrid energy system

ABSTRACT

Recently, the exploitation of renewable energies and technologies in order to reduce the restrictions of fossil fuels is the attention of energy managers and engineers. Additionally, energy production cycles based on solid oxide fuel cells (SOFCs) are known for their versatility in fuel intake. In this regard, in the current article the thermodynamic-conceptual assessment of a novel combined energy system (CES) based on biomass gasification is developed. The proposed CES is comprised of four main units: a biomass gasification unit, a reformer fuel cell unit (based on SOFC), a waste heat recovery unit (WHRU), and an ignition engine (homogeneous charge compression type). The biomass gasification unit is considered as a fuel supply unit of proposed energy process. A larger fraction of CES electricity is produced through the fuel cell unit. Moreover, additional electric power is produced through the ignition engine (IE) unit. The combustible fuel for IE unit is obtained during the chemical reactions of the fuel cell unit. Further, the WHRU is responsible for the heat recovery of the fuel cell and IE units, which balances the thermal power of the process. Embedding of a unit to recover the heat of the fuel cell units and the engine can be improving the performance of the cycle. The main goal of the article is to provide a thermodynamic-conceptual evaluation of the system considering energy, exergy, exergoeconomic, and environmental analysis to achieve a comprehensive feasibility study. According to the energy analysis, it was determined that the considered CES can produce around 1.09 MW of electricity and 0.36 MW of heat. Additionally, the values obtained for electrical and total energy efficiencies were 50.5% and 68.7%, respectively. The total exergy destroyed by the considered process and the total exergy efficiency were yielded as nearly 1.1 MW and 51.6%, respectively. Besides that, the specific cost rates of electric power yielded by fuel cell and IE units were almost 8.81 and 10.04 USD/GJ, indicating that the electric power produced through the fuel cell unit is a cheaper method. Moreover, compared to petroleum and coal-driven plants, the considered CES can reduce the amount of emitted CO₂ by nearly 47.7% and 62.4%, respectively.

KEYWORDS:

• Biomass gasification
• solid oxide fuel cell
• ignition engine
• combined energy system
• environmental
• exergoeconomic

Disclosure statement

No potential conflict of interest was reported by the author(s).